Chromecast Ultra profile doesn't support HEVC

@jonkv said:

Then Plex tries “direct stream”, AKA remuxing – it should be able to keep the video part of the stream as it is, but still transcode the DTS audio to for example AAC, which is much cheaper than video transcoding.

AFAIK if Plex is “direct streaming” then it is just repackaging the audio and video streams in a different container. If the audio needs transcoding then Plex has to use HLS for streaming, and this requires the video to be in H264 format. I had this experience in the past that even if the video is in a supported format (different from H264), if the audio needs transcoding then the video will transcode to H264.